Calix[4]resorcinarene Derivatives as High‐Resolution Resist Materials for Supercritical CO₂ Processing

Abstract

Advances in the microelectronics industry are continuously driven by employing new technologies. A recent development has been to use small-molecule photoresists (or resists) instead of conventional polymeric resists as the patterning material. [1][2][3][4][5] These small molecules known as molecular glass resists (MG resists) possess several intrinsic structural advantages as compared to their polymeric counterparts, such as small and uniform molecular size. Despite their small size, these molecules have the potential to function as high-performance patterning materials owing to their high glass-transition temperatures (T g ) and their ability to form stable thin films similar to polymeric resists. The small molecular cross-section of 1-2 nm afforded by these materials is expected to facilitate high-resolution patterning. Indeed, extensive theoretical studies have shown that a reduction in molecular size and dispersity will also improve other aspects of patterning performance. [6,7] The small size of MG resists has also enabled the use of dry processing techniques such as the supercritical CO 2 (scCO 2 ) development of photoresists. scCO 2 has shown promise as an environmentally friendly replacement for traditional development solvents.[8] The many advantageous properties of scCO 2 such as high diffusivity, absence of surface tension, and tunable solvent power indicate several potential benefits over traditional liquid solvents. However, previous CO 2 -soluble polymeric resists have required large amounts of undesirable fluorination to impart solubility. [9][10][11] Owing to their small size, MG resists may be soluble in scCO 2 without the need for fluorine. Indeed, it has recently been shown that non-fluorinated MG resists heavier than 1000 g mol À1 are significantly soluble in scCO 2 , [12] although the ultimate molecular-weight limit for such solubility has yet to be determined. In the first report of sub-50 nm pattern development using scCO 2 , hexa(hydroxyphenyl)benzene MG resists have been developed using scCO 2 under modest temperature and pressure conditions. However, hexa(hydroxyphenyl)benzene is such a specialized material that structural modification of this scaffold is extremely difficult, and therefore opportunities for further exploration of the solubility and other properties via structural variation are quite limited. Although phenolic MG materials have been shown to be scCO 2 soluble, recent investigations of selected phenolic MG resists have shown that because of the plasticizing nature of scCO 2 , [13] it is necessary that scCO 2 -soluble MG resists possess a high T g to enable high-resolution patterning. It is thus necessary to start with a high-T g system where the thermal and CO 2 solubility properties can be systematically optimized via modifying the same structural platform.In previous work, we have reported the very high-resolution capability of MG resists based on calix[4]resorcinarene (or resorcinarene) derivatives using extreme UV (EUV) lithography. [3] In order to extend the use of t...

In pursuit of Moore’s Law: polymer chemistry in action

“…It was the first report on the calixarene-based resist for EUV lithography, and 30 nm positivetone patterns were achieved. To expand the calix [4]resorcinarenesbased MGs, Felix et al 35 synthesized a family of calix [4]resorcinarene derivatives with variable size and different architectures (Figure 6b). Among the compounds studied in this work, the C-TMSB-4-R-100 tBoc was revealed to be the best candidate and achieved 70 nm patterns upon e-beam exposure.…”

Molecular Glass Resists as High‐Resolution Patterning Materials

“…Recent work also reports that calix [4]resorcinarene derivatives up to 2000 g mol À1 can be developed in scCO 2 with very high dissolution rates. [35] A calix [4]resorcinarene derivative with pendent trimethyl silyl groups has been developed to obtain line/space patterns of 70 nm. MG resists has provided the ideal platform for scCO 2 to prove itself as both an environmentally friendly and a high-performance solvent.…”

Molecular Glass Photoresists with High Resolution, Low LER, and High Sensitivity for EUV Lithography

“…Conventional reported MG photoresists are polyphenolic compounds, calix[n]arene, calix[4]resorcinarene derivatives, and so on . In this work, two novel bisphenol A‐based positive‐tone MG photoresists (BPA‐6 and BPA‐10, Scheme ) are developed and their thermal properties and lithographic performances have been evaluated in detail.…”